Superconducting magnets for very high fields: status in Japan

Three projects on superconducting magnets for very high fields are now in progress in Japan. The Japan Atomic Energy Research Institute constructed TMC-1 having an inner diameter of 600 mm which could produce 11.1 T by using a multifilamentary Nb₃Sn conductor. The National Research Institute for Metals has developed a multifilamentary Nb₃Sn wire with Ti doping and fabricated a high-stability superconducting magnet which will produce a magnetic field of 15 T in an 180 mm bore. Combined with this magnet, a new superconducting magnet system, which may break the field record in the superconducting state, is under construction. The High Field Laboratory for Superconducting Materials at Tohoku University constructed a hybrid magnet, in which a Nb₃Sn superconducting magnet was combined with a polyhelix type water-cooled magnet and produced a total magnetic field of 29.3 T in a 32 mm bore, where 10 T was produced by the superconducting magnet with an inner bore of 430 mm. The present status of these projects is briefly described.